Carbodiimide foams and improved process for preparing same

ABSTRACT

Rigid foam compositions characterized by carbodiimide linkages are prepared from the catalytic condensation of an organic polyisocyanate in the presence of a co-catalyst system consisting essentially of a mixture of 2,4,6-tris (dialkanolamino)-striazine and 1,3,5-tris(N,N-dialkylaminoalkyl)-shexahydrotriazine.

o 1 Tlmte States Patent 1191 1111 3,723,366

Kan 1451*ar. 27, 1973 [54] CARBODHMIDE FQAMS AND 2,941,966 6 1960Campbell ..260 2.5 IMPROVED SS OR 3,502,722 3/1970 Neumann ..260/566PREPARING SAME 3,462,381 8/1969 Eaton ..260/2.5 Y W 7 2,993,870 7/1961Burkus ..260/2.5 Inventor: Peter T. Kamwyandotte, Plymouth, 3,657,1614/1972 Bernard ..260/2.5 MlCh. 3,645,923 2 1972 Kan ..260 2.5 73,620,986 ll/197l Diehr ..260/2.5 3] Asslgnee z fizgg Corporamn3,580,868 5 1971 Diehr ..260/2.5

[ 1 Notice: The portion of the term of this W Primary Examiner-Donald E.Czaja pa n s q e to 1939, Assistant Examiner-C. Warren Ivy has beendlsclalmed- Attorney-Robert E. Dunn, Joseph D. Micheals, 22 r June 251971 Robert M. Phipps and Bernhard R. Swick Related U.S. ApplicationData Continuation-in-part of Ser..No. v28,555, April 13, 1970,abandoned.

References Cited UNITED STATES. PATENTS 9/1958 Campbell ..260/77.5

Rigid foam compositions characterized by carbodiimide linkages areprepared from the catalytic condensation of an organic polyisocyanate inthe presence of a co-catalyst system consisting essentially of a mixtureof 2,4,6-tris (dialkanolamino)-s-triazine and 1,3,5-tris(N,N-dialkylaminoalkyl)-s-hexahydrotriazine.

8 Claims, No Drawings CARBODIIMIDE FOAMS AND IMPROVED PROCESS FORPREPARING SAME CROSS-REFERENCE TO RELATED APPLICATION This applicationis a continuation-in-part of copending US. Pat. application Ser. No.28,555, filed Apr. 13, 1970, now abandoned and entitled CarbodiimideFoams and Improved Process for Preparing Same.

BACKGROUND OF THE INVENTION l. Field of the Invention The presentinvention concerns cellular foam compositions and methods of preparationtherefor. More particularly, the present invention concerns novelcarbodiimide foam compositions and methods of preparation therefor. Evenmore particularly, the present invention concerns novel carbodiimidefo'am compositions prepared from the catalytic condensation of anorganic polyisocyanate.

2. Prior Art In copending patent application U.S. Ser. No. 5,985entitled Carbodiimide Foam Composition and Process of PreparationThereof," filed Jan. 26, 1970 now US. Pat. No. 3,645,923, the disclosureof which is hereby incorporated by reference, there is disclosed thereinnovel rigid foam compositions characterized by carbodiimide linkages,which exhibit excellent flame retardancy and which are useful in mostareas heretofore reserved for polyurethane foams and the like. Thesefoams are prepared by catalytically condensing an organic polyisocyanatein the presence of a catalytically sufficient amount of a2,4,6-tris(dialkanolamino)- s-triazine catalyst. The condensationreaction is conducted at a temperature ranging from about 70 to 200 C.and preferably at atmospheric pressure. Although the method ofpreparation of these compositions is quite efficient and worthwhile, itis necessary to supply external heat. From a practical and economicstandpoint, it is desirable in many instances to prepare carbodiimidefoam compositions by a process which can be carried out withoutsupplying external heat.

SUMMARY OF THE INVENTION The present invention provides a process forpreparing rigid carbodiimide foams without supplying external heat byutilizing a unique co-catalyst system. The co-catalyst system whichaffords this result consists essentially of a2,4,6-tris(dialkanolamino)-s-triazine and a l,3,5-tris(N,N-dialkylaminoalkyl)-s-hexahydrotriazine, each being present incatalytically sufficient quantities. Thus, the present invention is seento provide rigid carbodiimide foam compositions by the catalyticcondensation of an organic polyisocyanate in the presence of acatalytically sufficient amount of a co-catalyst system consistingessentially of a 2,4,6- tris(dialkanolamino)-s-triazine and al,3,5-tris(N,N-dialkylaminoalkyl)-s-hexahydrotriazine wherein it is notnecessary to supply external heat.

For a more detailed description of the present invention reference ismade to the following detailed description and examples thereof.

DESCRIPTION OF THE PREFERRED EMBODIMENTS In accordance with the presentinvention, novel rigid foam compositions are prepared from the catalyticcondensation of an organic polyisocyanate in the presence of a2,4,6-tris(dialkanolamino)-s-triazine and 1,3,5-tris(N,N-dialkylaminoalkyl)-s-hexahydro'triazine co-catalyst system. Itappears that the foam forming reaction of the present invention proceedsin accordance with the following equation:

wherein R and R are each polyvalent organic radicals which may be thesame or different. The evolution of carbon dioxide by the reactionprovides a sufficient blowing agent for inducing and promoting foamformation. Thus, one readily apparent advantage of the present inventionis seen to be the elimination of the need for the addition of anyblowing agents to the reaction. Furthermore, the reaction is exothermicand the heat generated therefrom also promotes foam formation. But it isthe self-evolution of carbon dioxide which is essential in theformation-of the foams of the present invention.

The precise mechanism by which the co-catalyst system promotes foamformation in the present invention is not known. However, it is quiteplausible that'the carbodiimide linkages are formed indirectly fromisocyanurate ring formation. More particularly, it appears thatinitially some of the -NCO groups are trimerized thereby formingisocyanurate rings. This reaction is highly exothermic and the heatgenerated thereby works in conjunction with the triazine component ofthe co-catalyst system to promote the carbodiimide formation from theremaining NCO groups provided by the organic polyisocyanate. The basisfor this explanation lies inthe fact that hexahydrotriazines are knownto be isocyanate trimerization catalysts. See, for instance, Nicholas etal., Journal of Cellular Plastics, l (l), (1965). Furthermore, as notedabove, the triazines are known to be catalysts for carbodiimideformation.

As stated above, the foam compositions of the present invention arecharacterized by N=C=N linkages. Less dominant groups within the foamsare NCO and the above-noted isocyanurate rings or linkages. However, itis the carbodiimide linkages which are critical hereto and which impartthe excellent physical properties to the foam composition of the presentinvention.

The organic polyisocyanates which are advantageously employed in thepresent invention can be presented by the formula:

wherein R is a polyvalent organic radical selected from the group ofaliphatic, aromatic and alkylaryl organic radicals as well as mixturesthereof; and z is an integer corresponding to the valence number of Rand is at least 2. Representative of the organic polyisocyanatescontemplated herein includes, for example, the aromatic diisocyanates,such as 2,4-toluene diisocyanate, 2,6 toluene diisocyanate, mixtures of2,4- and 2,6- toluene diisocyanate, crude toluene diisocyanate,

methylene diphenyl diisocyanate, crude methylene diphenyl diisocyanate,and the like; the aromatic triisocyanates such as4,4,4"-triphenylmethylene triisocyanate; the aromatic tetraisocyanates,and the like; al kylaryl polyisocyanates such as xylylene diisocyanate;aliphatic polyisocyanates such as lysine diisocyanate methyl ester andthe like; and mixtures thereof.

These polyisocyanates are prepared by conventional methods known in theart such as the phosgenation of the corresponding organic amine.

Still another class of organic polyisocyanates contemplated by thepresent invention are the so-called quasi-prepolymers. Thesequasi-prepolymers are prepared by reacting an excess of any of theabove-enumerated organic polyisocyanates or mixtures thereof with aminor amount of an organic polyol. These polyols, which can be eitherpolyether polyols or polyester polyols, and their methods of preparationare well known in the art. The use of any one specific polyol is notcritical hereto, rather any polyol that can be used to prepare aquasi-prepolymer can be employed herein. Generally speaking, thequasiprepolymers are prepared by reacting an organic polyisocyanate witha minor amount, usually about 5 percent to percent by weight, based onthe weight of the polyisocyanate, of the polyol.

In the practice of the present invention, it is preferred to employ an80:20 mixture of 2,4- and 2,6- toluene diisocyanate. Alternatively, itis preferred to employ a mixture of 2,4- and 2,6-toluene diisocyanateand crude diphenyl methylene diisocyanate. This mixture generallyconsists of from about 50 to 95 percent by weight of the 2,4- and2,6-toluene diisocyanate and from about 5 to 50 percent by weight ofcrude diphenyl methylene diisocyanate.

The triazine component of the co-catalyst system employed in the presentinvention, as hereinbefore noted, consists of a2,4,6-tris(dialkanolamino)-striazine. Examples of the catalyst include2,4,6- tris(diethanolamino)-s-triazine, 2,4,6-tris(diisopropanolamino)-s-triazine,2,4,6-tris(dibutanolamino)-s-triazine and the like as well as mixturesthereof. In fact, any of the homologs of 2,4,6-tris(diethanolamino)-s-triazine exhibit utility in the presentinvention. It is preferred, however, to employ2,4,6-tris(diethanolamino)-s-triazine. Preparation of the triazinecomponent generally comprises condensing cyanuric chloride with theselected dialkanolamine in the presence of a neutralizing amount ofsodium hydroxide. Thus, for example, 2,4,6-tris(diethanolamino)-s-triazine is prepared from the condensation ofdiethanolamine and cyanuric chloride in the presence of a neutralizingamount of sodium hydroxide. The triazine compounds and their methods ofpreparation are more fully described by Kaiser et al., Journal oftheAmerica! Chemical Society, v. 73, p. 2984 195 l The hexahydrotriazinecomponent of the co-catalyst system consists of al,3,5-tris(N,N-dialkylaminoalkyl)- s-hexahydrotriazine. Representativeexamples of this component include, for example, l,3,5-tris(N,N-dimethyI-Z-aminoethyl)-s-hexahydrotriazine; 1,3,5-tris(N,N-dimethyl-3-aminopropyl)-s-hexahydrotriazine and the like;l,3,5-tris(N,N-diethyl-2-aminoethyl)-shexahydrotriazine;l,3,5-tris(N,N-diethyl-3- aminopropyl)-s-hexahydrotriazine and the like;1,3,5- tris(N,N-dipropyl-Z-aminoethyl)-s-hexahydrotriazine and the like;and so forth. In the practice of the present invention, it is preferredto employ l,3,5-tris(N,N- dimethyl-3-aminopropyl)-s-hexahydrotriazine.

The hexahydrotriazine component of the co-catalyst system is generallyprepared by reacting at a temperature of about 0 to 20 C. and atatmospheric pressure, equimolar amounts of a dialkylaminoalkylamine anda 37 percent aqueous solution of formaldehyde. More particularly, theamine and the formaldehyde are mixed together with gentle stirring atabout 0 C. Thereafter, and with continuous gentle stirring the resultingmixture is allowed to heat up to room temperature. The hexahydrotriazineis then recovered by first salting out the hexahydrotriazine from themixture with potassium hydroxide and then purifying by distillation.Thus, for example, l,3,5-tris(N,N-dimethyl-3-aminopropyl)-s-hexahydrotriazine is prepared by mixing together at 0 C.dimethylaminopropylamine and a 37 percent aqueous solution offormaldehyde. After reaching room temperature, the resultant mixture hasadded thereto potassium hydroxide and thereafter the hexahydrotriazineis separated and recovered by distillation. These hexahydrotriazinecomponents and their method of preparation are more particularlydescribed by Nicholas et al, supra, and by Graymore, Journal of theChemical Society, 1493 (1931).

Generally, the'co-catalyst system of the present invention is employedin a weight ratio of the hexahydrotriazine catalyst to the triazinecatalyst ranging from about 1:7 to 7:1. Preferably, a weight ratio ofhexahydrotriazine to triazine ranging from about 1:3 to 1:5 is employedherein.

In the preparation of the foam compositions of the present invention,generally, from about 0.1 to 10 parts by weight of co-catalyst system,per I00 parts by weight of organic polyisocyanate, is employed.Preferably, from about 0.5 to 3.0 parts by weight of co-catalyst system,per parts by weight of organic polyisocyanate, is utilized.

In a preferred embodiment of the present invention, where sufficientagitation is used to provide rapid dispersion and intimate mixing of thereactants, a blend of the two co-catalysts is employed and added to theisocyanate simultaneously.

Alternatively, and in another preferred embodiment of the presentinvention, the present foam compositions are prepared by addingtogether, with gentle or moderate agitation and without supplyingexternal heat, the organic polyisocyanate and the triazine catalyst.Thereafter, the hexahydrotriazine is added to the polyisocyanate and thetriazine. When using gentle agitation, it is preferred to combine theingredients in this manner for two reasons: (I) if the co-catalystsystem was used as a mixture and added together to the polyisocyanatethe reaction would be uncontrollable, this in turn would result in (2)non-homogeneous foam compositions. Thus, the co-catalyst system is addedto the polyisocyanate as two separate ingredients, when gentle agitationis used.

With the addition of the co-catalyst system to the polyisocyanate thereaction commences almost spontaneously and usually begins in about 2 to10 seconds. Commencement of the reaction is evidenced by an increase intemperature within the reaction vessel because of the exothermic natureof the reaction. Generally, the temperature will rise to a temperatureof about l to 200 C. In addition to the increase in materials and thelike. In addition, it has been found that these foam compositionsexhibit excellent flame retardancy and low smoke densities.

To more fully illustrate the present invention, followtemperature, thereaction is also evidenced by the ing are specific examples of thepresent invention evolution of carbon dioxide. After about 1 to 10 whichare not to be construed as being unduly limitaminutes the reaction iscompleted. The time necessary tive thereof. in the examples, all partsare by weight, to complete the reaction is, of course, dependent onabsent indications to the contrary.

the type and the amount of polyisocyanate and the amount of co-catalystsystem employed. 10 EXAMPLES l-18 Various other ingredients can beincorporated into 5 y the rigid foams of the present invention toenhance the A plurality of foams were properties thereof. For example,minor amounts of acprepahed at atmphenc pressure without P E or tiveingredients Such as organic polyols can be removing heat in accordancewith the following ployed. Generally, from about 1 to 20 parts by weightProcedm? l l d h of polyol per 100 parts by weight of polyisocyanate canTo a Sutab gg g wl 'P wit agltauo, be used herein. In addition, varioussurfactants, i was e f rt? fz j g plasticizers and filler materials canalso be employed 9 g fz a 1 i 1 o herein in amounts ranging from 1 to 75parts by weight 20 ms( ano l l' .cata 1 n ose stances wherein variousother ingredients such as filof each per 100 parts by weight ofpolyisocyanate.

The or nic l 1 th t b d t lers, plasticizers and the like were alsoemployed, they yo S ahcan e a i f i' e were added to the reaction vesselalong with the orfi i are g fi use f p ganic polyisocyanate and thetriazine catalyst. lme a otye-mentioneI puasi-prepo ymer. I xempmediately after these ingredients were placed and mg sue organ: p0 yo 5are the polyhydnc e mixed in the vessel, a catalytic quantity of a1,3,5- the Whether polyols prepared by oxyalkylatmgtris(N,N-dialkylaminoalkyl)-s-hexahydrotriazine compolyhydrt'c alcohols;polyoxyalklflene polyols; Polyester pound was rapidly added thereto.Almost immediately Prepared the macho" of a polycahboxyhc after thehexahydrotriazine came into contact with the and a P y y alcohol; hoxyalkylatloh ingredients in the vessel, carbon dioxide was evolved h fof the Polyester p y i h P P f therefrom accompanied with a rise intemperature taming p y and the Also lhehlded Wlthlh the within thevessel. This exothermic reaction reached a Posslble Polyois are themereapto'eompouhds Such as maximum temperature, in all instances, offrom about dithiols and the like as well as amino-compounds such 100 to200 C wi i a f seconds ft h h as ammo aleohols, ammes amides and theahydrotriazine was added to the vessel the reaction was RepresentativeOf the surfactants are the well-known completed and a foam characterizedcarbodiisilicon-based polysiloxane surfactants. id linka es was therebyobtained.

Filler materials such as calcium carbonate, barium Th following table,Table 1 Sets f th the sulfate, calcium oxide and the can also beemgredients used to prepare foams in. accordance ployed in the foampreparatiomAlso, plasticizers such 40 with the present invention. In thetable, except where as tris(beta-chloroethyl) phosphate and dioctylphthaotherwise indicated, the triazine component of the colate arecontemplated for use herein. catalyst system, denoted in the table asTDT, consisted The final foam products obtained by the practice of of2,4,6-tris(diethanolamino)-s-triazine and the hexthe present inventiongenerally have densities ranging ahydrotriazine component, denoted inthe table as from about 0.5 to 20.0 pounds per cubic foot and TDH, was1,3 ,5 -tris(N,N-dimethyl-3-aminopropyl):susually from about 0.8 to 16.0pounds per CUblC foot. hexahydrotriazme. Also, except where otherwise m-These foam compositions, which are rigid cellular dicated, the organicpolyisocyanate reactant, denoted plastics, are suitable replacements forthe heretofore in the table as TDI, was an 80:20 mixture of 2,4- andknown foams in many applications such as insulating 2,6-toluenediisocyanate.

4' V W i [Room temperature initiated earbodilmide foams] Isocyanatereactant lolyol reactant (iataltsst P] v S f 00.0, C3003, B11804 )nr851- urar- HS {LS X 7 cizer amt DPEDM filler filler 0112:, ExampleIsoeyanate Parts Pnlyol Parts 'IDT TDII (parts) (parts) (parts) (parts)(parts) (parts 0. 2: 0.25 50 0. 52 0.12 50 0. 0. 24 50 0.00 0.12 2.5 500. 70 0. 24 2.5 50 4 0.50 0.20 2.5 50 1.00 0. is 2.5 50 0. 70 0. 24 2.550 0. 70 a 0. 24 2.5 50 0. 70 0. 24 2.5 -10 .1 2-72 :2 t 0 00 n 0 5 0.70 0. 25 2.5 50 1 5 0.70 0. 24 2.5 50 5 0. 70 0. 24 2.5 as 1.50 0.48 2.5

[Room temperature initiated carbodiiinide foams] Isocyanate reactantPolyol reactant Catalyst (parts) Plasti- Surfaccizer tant 1 DPEDA 1Example Isoeyanate Parts Polyol Parts TDT TDH (parts) (parts) (parts) 1llastieizer is tris(bcta-chlorethyl)phosphate. 1 Surfactant is apolysiloxane surfactant. 3 l)lEDA=N,N-diphenylethylenediamine as areactive additive.

4 A solution of 2,4,6-tris(diethanolamino)-s-triazine indimethyliormamide. 5 lolyol A=A polyoxypropylene glycol having anaverage molecular weight of about 425 and prepared by oxypropylating apropylene glycol.

lolyol propylene glycol.

B=A polyoxypropylcne glycol having an average molecular weight of about775 and prepared by oxypropylating a I lolyol C=A polyoxypropyleneglycol having an average molecular weight of about 1,050 and prepared byoxypropylating a propylene glycol.

* lolyol l)=A pulyoxypropylene glycol having an average molecular weightof about 2,000 and prepared by oxypropylating a propylene glyeol Ml)l=(rude methylene diphenyldiisocyanate.

lrepolyrnei'=-An NCO-terminated prepolymer prepared by reacting in a :1weight ratio an 80:20 mixture oi 2,4-and 2,0- toluene diisoeyanate and apolyol consisting of a polyoxypropylene glycol having an averagemolecular weight of 500 prepared by oxypropylnting n propylene glycol.

EXAMPLES 19-22 These examples illustrate the preparation of acarbodiimide foam utilizing a blend of the co-catalysts in accordancewith the following procedure.

To a suitable reaction vessel equipped with agitation means was added anorganic polyisocyanate. While vigorously agitating the polyisocyanatethere was added thereto a blend of co-catalyst previously prepared bymixing the two co-catalysts together. The blend was immediatelydispersed in the polyisocyanate and almost immediately thereafter areaction began as evidenced by the development of an exothcrm and theevolution of carbon dioxide.

After a few seconds the reaction ceased and a rigid foam productcharacterized by carbodiimide linkages was obtained.

in preparing these foams, the surfactant and plasticizer, where used,were added with the co-catalyst blend, the surfactant and plasticizerhaving been previously premixed therewith to facilitate theirintroduction.

TABLE 11 parts of (Bo-catalyst system per parts of organicpolyisocyanate.

3. The process of claim 2 wherein the co-catalyst system is employed ina weight ratio of hexahydrotriazine catalyst to triazine catalystranging from about 1:7 to 7:1.

4. The process of claim 3 wherein the2,4,6-tris(dialkanolamino)-s-triazine is selected from the groupconsisting of 2,4,6-tris(diethanolamino)-s-triazine, 2,4,6-tris(diisopropanolamino)-s-triazine, and mixtures thereof.

5. The process of claim 3 wherein the 2,4,6-tris(dial-'kanolamino)-s-triazine is 2,4,6-tris(diethanolamino)-striazine.

6. The process of claim 3 wherein the l,3,5-tris(N,N-dialkylaminoalkyl)-s-hexahydrotriazine is 1,3 ,5-tris(N,N-dimethyl-3-aminopropyl)-s-hexahydrotriazine.

7. The process of claim 1 wherein the organic polyisocyanate isrepresented by the formula:

[ROOM TEMPERATURE INITIATED FOAMS FROM CO-CATALYST BLEND] Isocyanatereactant Catalyst (parts) Surfact- Plasti- Foam Exo- Isoant 5 cizcr 0density, therm, cyanate Parts TDT 3 TDl-I 4 (parts) (parts) lbs./ft. C.

l 100 1. 2 0. 6 0. 40 0. 80 l. 2 g 2 1.2 0.0 0. 40 0.80 2.1 176 g8 1.00.8 0.53 1.07 2.8 102 g8 2.4 1.2 0.80 1. 00 4. 7 127 1 An 80:20 weightmixture of 2,4- and 2,5-tolucno diisocyanatc. 1 Crude methylenediphenyldiisocyanate.

1,3,5-tris(N,N-diniethyl-3-aininopropyl)-s-liexaliydrotriazine. 5Surfactant is a polysiloxane surfactant.

6 Plasticizer is tris(beta-chloroethyl) phosphate.

wherein R is a polyvalent organic radical selected from the groupconsisting of aliphatic and aromatic radicals and z is an integercorresponding to the valence of R and is at least 2.

8. The process of claim 7 wherein the organic polyisocyanate is selectedfrom the group consisting of toluene diisocyanatc, methylene diphenyldiisocyanate, xylylcne diisocyanate, lysine diisocyanate methyl esterand mixtures thereof.

2. The process of claim 1 wherein the co-catalyst system is present in aweight ratio of from 0.1 to 10 parts of co-catalyst system per 100 partsof organic polyisocyanate.
 3. The process of claim 2 wherein theco-catalyst system is employed in a weight ratio of hexahydrotriazinecatalyst to triazine catalyst ranging from about 1:7 to 7:1.
 4. Theprocess of claim 3 wherein the 2,4,6-tris(dialkanolamino)-s-triazine isselected from the group consisting of2,4,6-tris(diethanolamino)-s-triazine,2,4,6-tris(diisopropanolamino)-s-triazine, and mixtures thereof.
 5. Theprocess of claim 3 wherein the 2,4,6-tris(dialkanolamino)-s-triazine is2,4,6-tris(diethanolamino)-s-triazine.
 6. The process of claim 3 whereinthe 1,3,5-tris(N,N-dialkylaminoalkyl)-s-hexahydrotriazine is1,3,5-tris(N,N-dimethyl-3-aminopropyl)-s-hexahydrotriazine.
 7. Theprocess of claim 1 wherein the organic polyisocyanate is represented bythe formula: R(NCO)z wherein R is a polyvalent organic radical selectedfrom the group consisting of aliphatic and aromatic radicals and z is aninteger corresponding to the valence of R and is at least
 2. 8. Theprocess of claim 7 wherein the organic polyisocyanate is selected fromthe group consisting of toluene diisocyanate, methylene diphenyldiisocyanate, xylylene diisocyanate, lysine diisocyanate methyl esterand mixtures thereof.